const int scan_zigzag[8][8] = {
  {0,  1,  5,  6,  14, 15, 27, 28},
  {2,  4,  7,  13, 16, 26, 29, 42},
  {3,  8,  12, 17, 25, 30, 41, 43},
  {9,  11, 18, 24, 31, 40, 44, 53},
  {10, 19, 23, 32, 39, 45, 52, 54},
  {20, 22, 33, 38, 46, 51, 55, 60},
  {21, 34, 37, 47, 50, 56, 59, 61},
  {35, 36, 48, 49, 57, 58, 62, 63},
};
const int scan_alth[8][8] = {
  {0,  1,  2,  3,  10, 11, 12, 13},
  {4,  5,  8,  9,  17, 16, 15, 14},
  {6,  7,  19, 18, 26, 27, 28, 29},
  {20, 21, 24, 25, 30, 31, 32, 33},
  {22, 23, 34, 35, 42, 43, 44, 45},
  {36, 37, 40, 41, 46, 47, 48, 49},
  {38, 39, 50, 51, 56, 57, 58, 59},
  {52, 53, 54, 55, 60, 61, 62, 63},
};
const int scan_altv[8][8] = {
  {0,  4,  6, 20, 22, 36, 38, 52},
  {1,  5,  7, 21, 23, 37, 39, 53},
  {2,  8,  19, 24, 34, 40, 50, 54},
  {3,  9,  18, 25, 35, 41, 51, 55},
  {10, 17, 26, 30, 42, 46, 56, 60},
  {11, 16, 27, 31, 43, 47, 57, 61},
  {12, 15, 28, 32, 44, 48, 58, 62},
  {13, 14, 29, 33, 45, 49, 59, 63},
};
